Television receiver



June 2, 1942. 4 M MESSNER 2,285,043

TELEVIS ION RECEIVER Filed- Aug. 22, 1936- www Patented June 2, 1942TELEVISION RECEIVER Application August 22, 1936, Serial No. 97,391 InGermany August 23, 1935 (Cl. Z50-27) Claims.

Television systems are known in which the current transmitted to thereceiver or reproducing station is periodically reduced, and preferablyreduced to zero, in order that at the receiver the well-known traversingaction of the cathode ray or beam shall be caused to synchronize withthe well-known scanning action at the transmitter. This method is theso-called gap synchronization.

In the receivers of these television systems it often occurs that theperiod of time necessary for accomplishing the return movement of thebeam is longer than the duration of the synchronizing gap. In such eventthe return movement of the beam will not be controlled to dark right tothe end, that is to say, the beam will not be invisible throughout theperiod of its return movement. As a result, unwelcome bright zones mayhappen to appear in the image.

In arrangements wherein no gap synchronization is used but in which, forexample, the usual graphic representation shows the synchronizingimpulses as surmounting the curve of the picture modulation, no controlto dark is ensured at all.

In order in any case to attain that the Braun tube, i. e, the cathoderay tube, is controlled to dark during the entire period of the returnmovement of its beam, it is proposed by the invention to block up duringthis period the receiver by which the intensity control of the Brauntube is eiected. This blocking action is performed by means of a voltagederived from the well-known generator of relaxation oscillations, thatis, oscillations whose graphic representation is saw-tooth shaped.

The drawing is a diagrammatic representation of an example of the novelarrangement.

The generator of relaxation oscillations comprises a charge condenser Cwhich is charged over a resistance W and is discharged over an electrontube R that represents the so-called relaxation tube. The condenser C ischarged over a longer period of time from a battery with the positivepole of which it is connected through resistance W than the period ofthe discharge, whereby the well-known sawtooth-shaped voltage variationsare produced. Included in the discharge circuit, that is, in the anodecircuit of the tube R, is a resistance V low as compared to W and fromwhich in accordance with the invention a voltage is derived and conveyedover a condenser Cl to the grid of an amplifier tube A vof the imagereceiver. This constitutes a blocking potential shunt for theray return.Additional amplier tubes may be connected to this tube A. The picturecurrents arriving from tube A act to accomplish the intensity control ofthe Braun tube B.

The circuit arrangement here shown ensures that owing'to the dischargeof the condenser C, that is to say, during the entire period of thereturn movement of the cathode ray of the tube B, the tube A and thusthe receiver is blocked up and tube B controlled to dark in this way.The potential set up in the resistance V is applied to the tube A overthe coupling condenser C1. During the charging period a comparativelyweak current flows, the resulting potential drop being rather low, andduring the instantaneous discharge heavy current flow takes place in thereversed direction. This heavy current causes considerable potentialdrop across resistance 9, and this potential is utilized for blockingthe tube A to prevent the flow of plate current, lThe control electrodeof the Braun tube will be blocked by the potential applied from theusual biasing battery. Therefore the return movement of the cathode raywill not be visible.

The arrangement by which the generator of relaxation oscillations andthe system that serves to deflect the cathode ray are interconnected isnot shown, as such arrangement is immaterial to the idea of theinvention.

The invention not only presents the advantage that each return movementof the beam is invisible, such movements being visible in priorarrangements from any cause, but yin a general manner has the advantagethat the screen on which the image is reproduced is controlled to darkwhenever the beam starts on the return movement, this mode being muchmore pleasant than if the bright screen shows itself.

What is claimed is:

1. In a television receiver, a cathode ray tube vadapted to move itsbeam of electrons to and fro,

a generator of electric relaxation oscillations having an outputcircuit, an electron tube amplia cathode ray beam during its deflectionin a denite direction comprising a cathode ray tube including means fordeveloping, modulating, and defiecting a cathode ray beam, electricalenergy storage means, means including a resistive member for linearlystoring energy in said electrical energy storage means, said member andsaid electrical energy storage means being serially connected, aunidirectional conductor having a space discharge path for dischargingthe stored energy, said unidirectional conductor having the spacedischarge path thereof connected substantially in parallel with theelectrical energy storage lmeans and a resistance in series, and meansconsaid resistance being connected to the cathode of the cathode raytube.

deflection comprising a cathode ray tube including means for developing,modulating, and deecting a cathode ray beam, a capacity, a pair ofresistive members connected serially with said capacity, meansforlinearly charging said capacity through said resistive members, athermionic vacuum tube having anode, cathode and at least one controlelectrode, said capacity and one of said resistive members beingconnected substantially in shunt with the anode-cathode path of saidthermionic tube, means for impressing Variations in the charge stored onsaid capacity onto the deflecting electrodes of said cathode ray tube,and means connecting the common terminal of the capacity and theresistive member which are connected in shunt With Y the anode-cathodecircuit of the tube to the 3. Apparatus in accordance with above claim Ye wherein said unidirectional conductor comprises a thermionic Vacuumtube having the anodecathode path thereof connected substantially inparallel With the serially connected electrical energy storage means andthe resistance serially connected thereto.

4. Apparatus for controlling the production of a cathode ray beam duringone direction of its modulating means of the cathode ray beam, the otherterminal of said resistance being connected to the cathode of thecathode ray tube.

5. Apparatus in accordance With'above claim wherein there is provided inaddition means for impressing re-current signals from an external sourceonto the control electrode-cathode circuit of said thermionic tube.

MAXIMILIAN lVLESSNER.

